Gas turbines include components, such as buckets (blades), nozzles (vanes), combustors, shrouds, and other hot gas path components which are coated to protect the components from the extreme temperatures, chemical environments and physical conditions found within the gas turbines. Certain coating systems, such as diffusion coatings, may be formed by applying a layer of coating precursor material to the area of a substrate to be coated, and subjecting the coating precursor material and the substrate to conditions suitable for forming the coating system.
The formation of coating systems may be incomplete or inefficient, however, due the interaction of the coating precursor material with the external environment in addition or in lieu of the interaction of the coating precursor material with the desired substrate. In one example, formation of a diffusion coating may be inhibited or incomplete due to the release of coating-forming gas or vapor from the coating precursor material to the exterior environment without the gas or vapor contacting the substrate surface to be coated. Further, such incomplete or inhibited coating may be exacerbated when the surface to be coated includes narrow channels, cracks in the substrate surface, or other reduced-access areas.